The present invention relates generally to methods of making low-fat, fat free, or full-fat food products, and products made according to the method, in which food pieces are subjected to a controlled application step of oil and can be subjected to enzyme and/or cation treatment, blanching and/or specific cooking and/or drying techniques, to provide for snack food products having the texture, flavor, and other characteristics of conventional full-fat fried products.
Snack food products typically are made by frying sliced vegetable pieces in hot oil so that the moisture content of the sliced food pieces is reduced to a very low level and fat content is raised exponentially. Such products generally have a characteristic crispness that adds significantly to its organoleptic desirability. Fried potato or apple chips prepared using conventional methods generally have a fat content from about 30 percent to about 40 percent by weight, a percentage of fat that is considered by some to be unhealthy if these types of products are broadly substituted for low-fat foods and consumption is significant over time. While such products are accepted in the marketplace, consumers' desire to lower their fat consumption, limits this acceptance.
Furthermore, the conventional methods generally used, require these foods to be fried at high temperatures that can result in the production of potentially deleterious by-products. Reports of such by-products in recent years have led to general concerns about both fried and baked foods, especially those containing high amounts of fats and carbohydrates. Reports of acrylamide formation, generally in proportion to the degree of browning of foods high in fats and carbohydrates, have raised significant concerns within the food industry, the potential for harmful effects of this particular processing by-product.
To address some of these concerns, efforts have been made to reduce the amount of fat in such snack food products, and more recently, to find ways to minimize formation of potentially deleterious substances such as acrylamide and the like.
In recent years, “light” chips have been made using synthetic oils/fat that is substantially non-digestible and consequently non-absorbable by the human body, e.g. OLESTRA™. These products have received limited acceptance due in part to off-flavors perceived by some reports of detrimental gastrointestinal side effects and an FDA requirement of a warning label on such products, providing information that such fat substitutes may cause gastrointestinal side effects such as loose stools and abdominal cramping and/or the inhibition of absorption of some nutrients.
While products such as potato and apple chips are typically made using conventional frying methods, snack food products made with other nutritionally beneficial vegetables and fruits such as carrots, squash, parsnips, yuccas, pears, and the like have not successfully entered the market substantially due to the lack of effective processing methods.
There have been numerous efforts in the past to reduce the amount of fat in snack foods such as potato chips, via various processing means. These methods have achieved limited success in reducing fat content while still achieving desirable taste. One example is by conditioning surfaces of the food pieces prior to frying in oil in order to reduce oil absorption during frying.
Another example of reducing fat content is preparing the food pieces with full-fat or near full-fat content through conventional frying methods, and to subsequently remove some of the oil, such as via centrifugal force or superheated steam. These methods tended to be complicated and expensive, are known to damage or otherwise undesirably alter the final product, and would typically remove only a small fraction of the oil, and less than the amount of oil removal desired.
Yet another method of reducing oil content involved alternative methods of drying the food pieces without frying in oil, such as microwave heating, convection ovens, fluidized bed dryers, and the like. Oil or fat was typically applied in a separate step, such as a spraying step, in order to achieve a desired flavor while providing for some control over the amount of fat applied to the food pieces. However, ideally the food pieces should be in a monolayer to ensure even application of the oil, which can be difficult and expensive. Alternatively, the oil can be applied in a spray drum, which can evenly distribute the oil, but generally must be applied after drying, which can result in less desirable taste and texture than when the oil is applied before drying.
Because of the difficulties in spraying the oil, oil can also be applied by immersing the food pieces in the oil without cooking the food pieces. It is considerably more difficult to control the oil uptake onto or into the food pieces through oil immersion. For example, the parameters that tend to affect oil uptake the most are immersion time and temperature. Low-temperature oil has a higher viscosity, and thus tends to more easily adhere to the food pieces, while higher-temperature oil is less viscous, and less likely to adhere, but will also tend to be more likely to penetrate the surface of the food pieces, resulting in higher oil uptake. A food piece that has been fully immersed in oil of any temperature for any length of time will emerge with a minimum carry-over of oil that adheres to the surface of the food piece. For example, for potato slices the carry-over can be 5-12% of the weight of the slice, depending on slice thickness. After subsequent drying the percentage of oil by weight can be comparable to, or only modestly below, the oil take-up via traditional frying methods. Excess take-up of oil via the immersion method can be partially controlled by a subsequent oil removal step, such as gravitational draining, water sprays, or pressurized air jets. These methods, however, can also be difficult because of the need to monolayer the food pieces to ensure even removal of oil. The oil removal also adds another step to the process.
Roan (U.S. Pat. No. 4,058,631) discloses a method of making fried food in which raw food product is treated with an aqueous solution of an enzyme, such as alpha amylase, for a period of time sufficient for the enzyme to penetrate and coat the surface of the food, and thereafter the food product is deep fried. Roan indicates that when the surface of a raw, starchy food product is coated with an aqueous solution of alpha amylase prior to frying, less fat is absorbed in the food during frying than occurs without the enzyme treatment, and the flavor of the fried food is improved.
Dreher et al. (U.S. Pat. No. 4,756,916) discloses a process for producing low oil potato chips comprising washing potato slices with an aqueous solution, and applying oil to the washed slices to coat the slices with oil. The oil-coated slices are arranged as a monolayer on an endless conveyor belt, blanched at a temperature between about 160° F. and 212° F., and then baked at a high temperature of at least about 390° F. but below the smoke point of the oil, to partially dry the slices by reducing the aqueous moisture content of the slices to about 10-20% by weight. The partially dried slices then are further baked at a lower temperature of about 290°-320° F. to finish drying the slices by reducing the aqueous moisture content of the slices to about 2% by weight or less, to produce a product having an oil content of between about 10-25% by weight.
Laufer (U.S. Pat. No. 5,292,540) discloses a process for preparing potato chips comprising the steps of washing potatoes to remove foreign matter from the skin thereof, cutting the potato into thin slices, baking the slices for a period of about six to twelve minutes within a temperature range of about 250 to 500° F., and heating the slices in a microwave oven for about two to seven minutes.
Yamashita (U.S. Pat. No. 5,312,631) discloses a method for preventing cut pieces of agricultural products from sticking to each other during the steps of drying and cooking, which includes washing the cut pieces with, or immersing the same in, a solution of an amylolytic enzyme, or an acidic or alkaline aqueous solution. The cut pieces are blanched prior to enzyme treatment.
Zussman (U.S. Pat. No. 5,370,898) discloses a cooking process for food chip products that does not involve oil-based cooking. Food slices are washed with water to remove extractable surface starch, multi-layered, transported to an oven, and baked in a fluidized bed of hot air or steam. The baking process is a multi-step process, whereby the food slices are exposed to a higher pressure in a first zone for several minutes to ensure that the individual food pieces are separated. The pressure is then lowered in a second zone for a second period of time. Similarly, in a third zone the pressure is reduced for a predetermined period of time to finish cooking the food products. Thereafter the chips are air-dried or finished in a dryer.
Lewis et al. (U.S. Pat. No. 5,441,758) discloses the preparation of low-fat or fat free potato chips or straws by a process comprising slicing potatoes to form slices or straws, blanching the sliced potato, and treating the slices during or after blanching with a high temperature amylase enzyme to prevent later sticking together of slices during processing. The slices are thereafter dehydrated at 158° F.-212° F. content of 9% or lower. The dehydrated potato pieces are then rehydrated to a moisture content of 12% to 30%, and thereafter toasted to about 2% moisture at a temperature of 140° C. to 220° C. The use of a high temperature amylase is required so that the enzyme remains effective during processing, and is not inactivated by the blanching step. Lewis et al. discloses that a small amount of oil may be added at any point in the process, “but preferably just after toasting.”
Petelle et al. (U.S. Pat. No. 5,470,600) discloses a method of making fat-free potato chips, by initially cooking potato slices in a three zone primary oven, by first radiant heating the slices and then subjecting the slices to two successive stages of forced air heating to reduce the moisture content of the slices to near a final moisture content. Petelle et al. further discloses independently controlling the time duration in each of the three zones, simultaneously forcing the air into the top and bottom surfaces of the slices in the primary oven to a near final moisture content of about 15% by weight, independently controlling the time duration of the slices in the dielectric heater to a final moisture content of about 7% by weight using wavelengths of about 65.8 feet at a frequency of about 15 mhz, and allowing the slices to successively, increasingly pile up in the last two forced air stages and the dielectric heating stage.
Benson et al. (U.S. Pat. No. 5,603,973) discloses a process for making potato chips without the use of oil, wherein whole potatoes are cut into discrete slice pieces which are washed to remove starch or debris from the slice surfaces. The slices are arranged in a single layer and the surface water is removed from the slice surfaces by exposing them to blasts of air and suction. Alternatively, the slices may be washed in warm water at a temperature of about 130° F. to preheat them. The slices are transferred to a heated conveyor to enter an infrared zone for exposure to high intensity infrared energy for a short period of time, less than 25 seconds, effecting a blanching of the slices and quenching of naturally-occurring deleterious enzyme action. In a subsequent step, dry air is impinged upon the slices from above and below to reduce the water content below 35% by weight. The slices are accumulated in a multi-layer pack and dried in moving air until moisture content has been obtained to a level on the order of 0.5% to 2%.
Wiedersatz (U.S. Pat. No. 5,858,431) discloses a method for preparing fat-free snack chips, comprising preparing slices of raw food product, which are subjected to a high intensity air knife arrangement to remove surface moisture, then exposed to a hot air fluid bed impingement including multiple dual-zone hot air fluid bed impingement ovens operating under different predetermined conditions. In the preferred embodiment, the slices are exposed to two dual-zone hot air fluid bed impingement ovens, the first oven having a conveyor belt transporting slices through the oven at a speed of 2.5 to 3.0 feet per minute and operating at 500 to 525° F. (zone 1) and 450 to 500° F. (zone 2), and the second oven having a conveyor belt operating at a speed of 1.5 to 2.0 feet per second and at 350 to 400° F. (zone 1) and 300 to 350° F. (zone 2). The first impingement oven of the preferred embodiment removes approximately 50 to 60 per cent of the moisture in each slice, while the second impingement oven of the preferred embodiment removes approximately 20 to 30 per cent of the remaining moisture. The slices may then have oil and/or seasoning applied thereto, and are passed to a combination microwave and hot air dryer which removes entrained moisture without scorching the chips.
Xu et al. (U.S. Patent Publication No. 2002/0004085) discloses methods for producing a consumable product from potatoes, comprising: (a) treating a potato substance with an effective amount of one or more exogenous enzymes selected from the group consisting of an amyloglucosidase, glucose oxidase, laccase, lipase, maltogenic amylase, pectinase, pentosanase, protease, and transglutaminase, and (b) processing the enzyme-treated potato substance to produce a potato product. In one embodiment, blanching of the potato substance may occur prior to enzyme treatment. The processing step may include partial dehydration to reduce the initial moisture content by about 5-30% prior to frying in oil or baking.
Despite the many advances in the processing of snacks and chips, there nevertheless remains a need for improvements to these products, and the processes for making them, characterized by improved crispness, mouth feel and flavor properties, reduction of fat content and overall improvement in nutritional profile, including minimization of exposure to conditions that can result in the formation of potentially deleterious by-products. These all require processes that are feasible, efficient, manageable, and are practically and economically scalable for production at output levels necessary for product commercialization in an adequately fuel efficient production environment.